from fastapi import APIRouter, Depends, Query
from sqlalchemy import and_, or_, select
from sqlalchemy.ext.asyncio import AsyncSession

from ..cursors import decode, encode
from ..db import get_session
from ..models import Check
from ..schemas import ID_PATTERN, ChecksPage, CheckState
from ..timeutil import to_utc

router = APIRouter()


@router.get("/checks", response_model=ChecksPage)
async def list_checks(
    agent_id: str | None = Query(default=None, max_length=128, pattern=ID_PATTERN),
    cursor: str | None = Query(default=None, max_length=512),
    back: bool = Query(default=False),
    limit: int = Query(default=100, ge=1, le=500),
    session: AsyncSession = Depends(get_session),
) -> ChecksPage:
    # PH-review: bidirectional cursor. Natural sort is ASC (agent_id, check_id).
    if back:
        stmt = select(Check).order_by(Check.agent_id.desc(), Check.check_id.desc())
    else:
        stmt = select(Check).order_by(Check.agent_id, Check.check_id)
    if agent_id is not None:
        stmt = stmt.where(Check.agent_id == agent_id)
    if cursor is not None:
        last_agent, last_check = decode(cursor, 2)
        if back:
            stmt = stmt.where(
                or_(
                    Check.agent_id < last_agent,
                    and_(Check.agent_id == last_agent, Check.check_id < last_check),
                )
            )
        else:
            stmt = stmt.where(
                or_(
                    Check.agent_id > last_agent,
                    and_(Check.agent_id == last_agent, Check.check_id > last_check),
                )
            )
    rows = (await session.execute(stmt.limit(limit + 1))).scalars().all()
    has_more = len(rows) > limit
    rows = rows[:limit]
    if back:
        rows = list(reversed(rows))
    next_cursor: str | None = None
    prev_cursor: str | None = None
    if rows:
        if back:
            next_cursor = encode(rows[-1].agent_id, rows[-1].check_id)
            if has_more:
                prev_cursor = encode(rows[0].agent_id, rows[0].check_id)
        else:
            if has_more:
                next_cursor = encode(rows[-1].agent_id, rows[-1].check_id)
            if cursor is not None:
                prev_cursor = encode(rows[0].agent_id, rows[0].check_id)
    items = [
        CheckState(
            agent_id=r.agent_id,
            check_id=r.check_id,
            status=r.status,
            last_observed_at=to_utc(r.last_observed_at),
            exit_code=r.exit_code,
            incident_key=r.incident_key,
            summary=r.summary,
        )
        for r in rows
    ]
    return ChecksPage(items=items, next_cursor=next_cursor, prev_cursor=prev_cursor)